This invention relates to apparatus for reading, writing and storing magnetic data, and more particularly to a means for mounting a tape-automated bonded preamplifier to the substantially rigid arm supporting a magnetic transducing head.
A well known technique for increasing the data storage capacity of magnetic disc drives is to provide a series of rotating discs in spaced apart, stacked relation, along with a matching series of transducing head and support arm assemblies disposed for either linear or rotary transducing head movement with respect to the recording surfaces of the discs. Typically, one of the head and arm assemblies reads servo or positioning information on one of the recording surfaces dedicated to storing positioning information, while the remaining recording surfaces and accompanying head and arm assemblies are used to read and record working data. The positioning transducer and surface are employed to guide the remaining transducing heads as they read and record data. This of course requires a stable positional relationship among the servo head and data heads.
A flexible electrical circuit normally is used to transmit the electrical pulses between each head and other circuitry in the disc drive. A preamplifier, usually an integrated circuit chip mounted with respect to the flexible circuit and transducer support arm, insures that signals of sufficient amplitude are provided at the head. The preamplifiers give rise to a problem, however, particularly when the transducer support arms are constructed of aluminum or other material with a relatively high coefficient of thermal expansion. In particular, heat generated by each preamplifier causes thermal expansion in its associated transducer support arm. The varying degrees of thermal expansion cause a variance in length among the support arms, resulting in misalignment of the transducing heads.
One known approach to counteract thermal expansion is to mount the preamplifier chip within a dual-in-line package (DIP), using the metal leads of the package to mount the package in spaced apart relation to the support arm. This is relatively expensive compared to other methods, for example tape-automated bonding, and is subject to severe spatial limitations in typical disc drives. Another approach, shown in U.S. Pat. No. 4,658,331 (Berg), attaches a chip to a plate with a thermally conductive epoxy adhesive. Elastomer pads maintain the plate and chip spaced apart from a circuit board, and the plate tends to conduct heat away from the circuit board. This support means is somewhat large and bulky in the spatially limited disc drive environment, and would interfere with the wire bonding of chip pads to the flex circuit.
Therefore, it is an object of the present invention to provide a means for thermally isolating a transducing head support arm from heat generated by a preamplifier mounted to the arm.
Another object is to provide a low cost manner of mounting a preamplifier to a transducer support arm that minimizes thermal expansion of the arm.
Yet another object is to provide a multiple-stage configuration for supporting a tape-automated bonded preamplifier chip with respect to a transducer support arm, particularly well suited for thermally isolating the arm and dissipating heat generated in the preamplifier.